Apparatus for railway train communication systems



Oct. 25, 1938. w. P. PLACE ET AL 2,134,415

APPARATUS FOR RAILWAY TRAIN COMMUNICATION SYSTEMS Filed Aug. 11, 1937 5 Sheets-Sheet l v H91. A @58 QJSQD 2pliii; W 3 2625 r 2. l i J INVENTOR and Lars 0 G ozzdahl.

771E113 ATTORNEY Willa d 1? Place, Pau Z N BassaPz' Oct. 25, 1938. w. P. PLACE ET AL APPARATUS FOR RAILWAY TRAIN COMMUNICATION SYSTEMS Filed Aug. 11, 1937 3 Sheets-Sheet 2 Fig. 6.

Fly:

' INVENTOR I Willard 1? Place, Rqul Nfl m LY. w R Hm T A & mm @Y B d w Oct. 25, 1938.

w. PQPLACE ET AL 34,416 .APPARATUs FOR RAILWAY TRAIN COMMUNICATION SYSTEMS Filed Aug. 11, 1937 5 Sheets-Sheet 3 INVENTOR 0 4 Willa d PPZace, Paul Nfiossa t 9 I and LmsO. ndahl.

. I9- flY THEIR ATTORNEY Patented Oct. 25, 1938 I "2,134,416 APPARATUS FOR RAILWAY TRAIN co r- "MUNICATION SYSTEMS Willard if; Place; t West :De'er Township, he y ram '0. (ironam, *Pittstqrgh, r The Union "'8; Sig'jlial 'Cdlilli "Valle, 'Pai, a corporation Tif Al pl ication August 11,

9 Claims.

Our invention relates to apparatusfor railway train communication systems, and particularly "to apparatusfor railway train telephone systems. We shall describe certain forms of apparatus embodying our invention, and shall then point out the novel features thereof in claims. a

A feature of our invention is the provisionof novel and improved train-carried apparatus .for reception of communication current in electrified territory of a railway with minimum annoyance due to noise energy. A further feature of our invention is the provision of receiving apparatus for railway train communication systems which canbe set either for best operation in electrified territories or for best operation in steam ,territories. Other features and advantages of our invention will appear as the specification progresses. p i In railwaytrain communication systems, it has been proposed to include the track rails in the circuit used for transmitting the communication current between a station located on a train and another station such as, for example, W a wayside station or a station located on another train or on a second Vehicle 'of the same train. When the two stations are locatedon the same train, they may, for example, be located on the locomotive and caboose of a freight train. To send current from a location, an electromotive force corresponding in frequency to that of the communication current is produced in the track rails, and as a result of such electromotive force communication current flows in the rails from the point where the electromotive force is produced by virtue of the rail-to-ground impedance and the ground path, This communication current fiowing'in the rails causes an energy transfer to be effected to neighboring parallel conductors by virtue ofthe distributed conductance and distributed mutual inductance between the rails and such conductors. Such energy transfer causes, in turn, communication current to flow in the paralleling conductors by virtue of their distributed impedance to ground. In multi track rail ways, the track rails of the tracks other than the rails of the track to which the current is originally supplied serve as conductors for carrying the communication current] Especiallyisthis true 50 in electrified zones where the rails are cross com nected and the rails of the different tracks all serve as apart of a common frail return circuit for the propulsion current; Hence, communication current supplied to the rails of any one track of a multi-track railway is present in the rails (oil-2 16 8) adjacenttracirsand other paralleling conductors.

I5 teleehen sees: infants items, it has beerr proposed to a carrier telephone current, t

the carrier of whichjsoi a frequencyhigh enough 3 99 tant ellv. r ev rem erf en eby current. let, comm al. newe fr c h g I QH h in a o e th h h s o c r quenc es in be t ansmit di n ew enou h o; be. s b t ni e ri ee fr m leetrem n ic w v r i Ejor ex an ple, the telephone current may vbe the im -Q 1 si ev bend ei a Q r erpi 7000 cy le r secq i nmpdl le edlw h m uencies exten ing from 500' to 2500 cycles, the telephone current thus-having a frequency range of 7500 to 9500 le e e dh n the i in e p rat s- In general.

it .b i% 1 .11 2, u h ex r neeu ma fields are strongest in the neighborhood of the Z ilT .hlf lui tiheore etl r l on y to noise energy p kedup by a train-carried inducfe a iess er, ent hesitie i f nd o on the train an is ordinarily the best for an inlel i t iflq er lte iese fle m lt wt r lw y, especially where alternating current is used for n s e l r m. WQQ QE EQQ c rrent i fr e cy components that may produce noise in the resurpri es. theme neti fi mtr sultin 9iY 1 ePR 1etus e t e r nh n system, 7

and wehave f nd that suc h noise energy is presexit for allpos tions within the clearance limits railwfis trains and within which limits any train-carriedinductor' must, of course, be mountailw'ay an effective posied inductor is the roof I t e inductors disposed in a c we relationship to the U AIter a great deal of I alori'g electrifi d zones, wehavediscovered that with an inductor carried. at the s,as',-well as t the rails to around fourteen inches.. In our explorations we have discovered that best results are. obtained when the inductor is positioned,attheheight of the order of ten inches. It will be understood," therefore, that the positionof thefinductor is'an essential element but that our -i1iventidnis not limited to any exact height above the top of the rails for the inductor and a height of the order of ten inches is preferred; To illustrate the ad-' vantage obtained for an inductor positioned according to our discovery, under certain given operating conditions the noise energy for a horizontal inductor positioned above the rails at the height of the order of ten inches was reduced to about one-tenth of that picked up by the inductor mounted at the same height and disposed in a vertical plane. The telephone energy picked up by the inductor positioned at the height of ten-inches above the top' of the rails in a horizontal plane was" reduced to about one-half of that picked up by the inductor disposedin the vertical plane, and thus'the net advantage for the inductor in a horizontal plane at a height of the order of ten inches above the top of the rails was of the order of five.

According to our discovery, we provide traincarried communication receiving apparatus comprising a pair of inductor coils mounted on a vehicle of the train, one centered over' one rail at the height preferably of the order of ten inches and the other centered'in -like manner over the other rail. Each of thetwo inductor coils possesses relatively low'mutual induction with the rail directly beneath but relatively high mutual induction with the other rail of the same track and with the rails of adjacent tracks. Such inductor coils pick up telephone energy of sufiicient magnitude thattelephorie communication can be satisfactorily accomplished with minimum noise interference. When thecaboose or other vehicle of the train on which the com munication equipment islocated is'to be operated over both steam and electrified-zones of a railway, the receivingapparatus of our'invention is preferably provided with two pairs of inductor coils, one pair mounted above the rails in the manner set forth above for best operation as found to exist in electrified zones and the other pair of inductor coils mounted '-relatively' high (roof) on the vehicleand in a verticalplane for best operation'as found to exist insteam territory.

For a better understanding of our invention, reference may be hadtc the accompanying drawings in-which Fig. l'is a diagrammatic view of a stretch of electrified territoryof a four-track railway, the general distribution-of the'propulsion current in the track rails being illustrated. Fig. 2 is a diagram illustrating the magnetic fieldscreated by the'propulsioncurrent'for the railway of Fig. 1' and the relationship of such magnetic fields with respect to a pair 'of traincarried inductor coils embodying our jinvention. Fig. 3 is a diagrammatic view of the stretch of railway of Fig. 1' with the general distribution of communication current illustrated when a train occupies a particular one of the tracks. Fig. 4 is a diagram illustrating the inductive relationship of train-carried inductor coils embodying our invention with respect to the magnetic field created by the communication current under'the operating conditions of Fig. 3. Fig. 5 is adiagrammatic view of a preferred form of receiving apparatus embodying our invention. Fig. 6 is a diagrammatic view of a modification of theapparatus of Fig. 5 and which apparatus ,also embodies the invention. Figs. '7, 8 and 9 are diagrammatic views of train-carried apparatus embodying the invention for operation over either electrified territory or over steam "territory.

In each of the several views like reference characters designate similar parts. Referring toFig. 1, the reference characters I.W,; 3W, 2E and 4E represent the tracks of a four-track railway, tracks IW and 3W being ordinarily used for westbound trafiic and tracks 2E and 4E for eastboundtraflic as indicated by double pointed arrows. As here shown, the track rails of each track are divided by the usual insulated rail joints to form track sections as required for double rail track circuits for a wayside and/or cab signal system. Taking the eastbound track 2E, for example, three full sections 2E2, 2E3 and 2E4, and the adjacent ends of two sections 2E1 and 2E5 are shown, and it will be understood that the full length of track 2E is formed into similar consecutivetrack sections. Inlike' manner; the other tracks are formed into consecutive-track sections. An impedance bond isprovided at each insulated rail joint location inaccordance with usual practice for conducting propulsion current around the insulated rail joints but substantially blocking the flow of the track circuit-current of the signal system. Again looking at track 2E by way of example, impedance bonds |0,fl I, I2 and [3 are provided one at each junction of the tracksections.

The track rails'ofeach' of the four tracks are includedin a common rail return circuit for the propulsion current .by means of cross connections or bonds interposed between the mid terminals 0f the various impedance bonds. The particular arrangement of cross connections is immaterial and is shown in Fig. 1 as that found in present-day use. 1 At location A, the mid terminals of the'impedance bonds for the four tracks are all connected by a cross connection M, which is also connected with a ground electrode l5. At the next insulated rail joint location B to the left, no cross connections are used. At the next location C tov the left, a cross connection I6 is connected between the mid terminals of the impedance bonds of tracks IW and 3W, and. a cross connection I1. 'is connected between the mid terminals of the impedance bonds for the tracks 2E and 4E, the cross connection I! being further connected with a ground electrode l8. At the next location Al to the left, the arrangement :is similar to that at location A. I

It is'to be understood that our invention is not limited to a four-track railway or to a railway the track rails of which are formed into insulated track sections. As a matter of fact, the insulated rail joints may be so arranged as ,toform the rails of each track into sections as requiredto provide, single rail track circuits for the vwayside signal system. The track layout of Fig. l'willserve, however, to illustrate the many plaoes where' the invention is useful.

Propulsion current :is supplied. to: the. tracks .of Fig. 1 by vagenerator G, one terminal of which is connected through the usual :feeder network (notshown) with the trolley wires "forcth'e :different tracks, only the one trolley wire TWI associated with track 1W being shown for the sake of simplicity, and it will be understood that each of the other tracks is provided with a similar trolley wire. The other terminal of the generator G is connected-with each track rail of the four tracks over-a crossv connection l9. The propulsion current supplied by thes'generator G may be either direct current or alternating current, and it is here assumed to be an alternating current of 25 cycles per second.v

A train FT is indicated schematically on track IW, the two ends of. the train occupying the sections IW3 and IW4, respectively. The train FT may be of any makeup and, for example, it may be a freight train of which 20 designates the forward vehicle or locomotive and 2| designates the rear vehicle or caboose. The reference character 22 designates the controller mechanism of the locomotive 20 for governing the supply of current from the trolley. wire TWI to the motors 23 for driving the locomotive, current being collected from the trolley wireTWl by the usual trolley wheel or ,pantograph col: lector 24. Propulsion current used to drive the locomotive 20 returns to the generator G over the rail return circuit, equalizing in the rails of the different tracks due to the cross connections. Furthermore, the propulsion current used by other locomotives, not shown, on the other tracks, either within the stretch shown in Fig. l or outside of said stretch, returns to the generator G through the rail return circuit. Single pointed arrows have been added to Fig. 1 to indicate the general distribution of the propulsion current, the direction of the arrowsr 'ndi cating the relative direction of the flow of current at a given instant.

Because the propulsion current is strongly in clined to be distributed equally in all the rails of the track, and is also distributed to the different trolley wires through the medium of the usual feeder system, a strong magnetic field is created. Such magnetic field has frequencies equal to the fundamental and ,harmonic .fre: quencies of the propulsion current and contains other frequencies such as those due to commutation at the locomotive motors Looking at Fig. 2, the lines 25 illustrate the magnetic .flu'irlines created about each individual rail of the four tracks by the propulsion current, the arrows placed on lines 25 indicating the direction of the flux lines at a given instant. The lines '26 illustrate the magnetic flux lines encompassing the two rails of each of the four tracks due to the propulsion current flowing in both rails of each track in the same direction, and again, the direction of the arrows placed on these lines indicate the direction of the flux at agiven instant. The lines 2] illustrate the magnetic flux which encompasses the fourtrack'sas a whole. The lines 38 and 39 indicate the magnetic fluir' lines created about the trolley wires "of the dif-l ferent tracks. It is clear that the magnetic fields created by the propulsion current,.as illustrated in Fig. 2, permeate the space occupied energy thus-induced in such. inductor having components corresponding :in frequencies .to- :the'

These :inductor :coils are disposed .with their a-Xes vertical. We have "found that inductor coils. .CI. and C2 disposed in a horizontal plane (axes -perpendicular).,.a few inches above the top Oflthe rails, as s'hownin Fig. 2, .give aminimum response to the influence of the magnetic field created by the propulsion current. The function of the inductor coils :Cl and C2 and their relationship to the propulsion :current magnetic field will be further discussed hereinafter.

Referring to Fig. 3, the track layout and the freight train FT occupying the Westbound track IW are the same as in Fig. 1. Looking at the train the locomotive 20 and the caboose 2-1 are provided with communication equipment including transmitting apparatus. TA on the locomotive and receiving apparatus RA on the caboose. The transmitting apparatus TA and the receiving apparatus RA may be any one of several well-known forms and each is shown conventionally for the sake of simplicity. It is deemed sufficient -for this application to but. Assuming.

briefly describerthese apparatuses. telephone communcation :is to be effected between the locomotive 20 and the caboose 2| by means of the upper side band telephone current referred to hereinbefore, the transmitting apparatus TA includes a source of carrier current of 7000 cycles per second, means for modulating the carrier by voice frequencies, and a filter for selecting theupper side band and substantially suppressing the lower side band and the carrier. The output side of the transmitting apparatus TA is conductively coupled with the track rails over wires 28 and 29 which are connected with the rails by being connected to the journal bearings of the rear and forward pairs ;of wheels of the locomotive, respectively. In order to effect a more equal distribution of the communication current supplied to the track rails, each of the wires 28 and 29 would be connected in multiple to both journal bearings of the respective pair of wheels. I Hence, when the transmitting apparatus TA is made active, communication current flows in that section of therails between the forward and "rear pairs of locomotive wheels. This communication current produces an electromotive force across the section of rails be tween the forward and rear pairs of locomotive wheels,"a nd as a result of such electromotive force the'telephone currentfiows in the rails bothin advance of andto the rear of the locoother tracks due 'to the cross connections be-v tween the tracks and due to the distributed mutual inductance and conductance betweenthe rails of the track IW occupied by the train and the rails of the other tracks. Arrows have been added to Fig. 3 to illustrate the general distribution of the telephonecurrent when supplied to the track IW adjacent thelocomotive 29. These arrows would indicate the direction of the flow of current at a given instant. As the train FT advances, distribution of the telephonecurrent not only advances with the train but also changes due tothe relative position of theloco- .motive with respect to the cross connections,

etc. A portion of the communication current flowing in the track rails will reach the location of the caboose 2|. The magnitude of the current adjacent the caboose depends upon the attenuation of the current due to ballast resistance and other conditions. At a distance of the order of one mile (usual freight train length), the magnitude of the telephone current is sufficient for effective telephone communication. It is clear from Fig. 3 that by the very nature of the circuit involved the telephone current is not distributed in'the rails of the several tracks in an orderly fashion. At least, it is not distributed in an orderly fashion to the same extent as the propulsion current; It will be understood, of course, that our invention is not limited to use of a carrier telephone current of frequencies here assumed, and other frequencies can be used.

The receiving apparatus RA includes an amplifier and a demodulator which are operative when carrier telephone current is supplied to its input terminals to produce in its output circuit a current containing the voice frequencies only. 'Referring to Fig, 5 as well as to Fig. 3, theinput circuit for the receiving apparatus RA includes two inductorcoils Cl and C2. As viewed in Fig. 5, this input circuit can be traced from the-lower left-hand input terminal of the receiving apparatus RA over wire 3!, condenser 32, wire 33, coil Cl, wire 34, coil C2, wire 35, condenser 36, and wire 31 to the lower right-hand input terminal of the apparatus RA. The output circuit of the receiving apparatus RA is connected through a transformer Tl with the operating winding of a loud speaker LS, as will be readily understood by an inspection of Fig. 5. Hence, telephone current picked up by the inductor coils Cl and C2 is amplified and demodulated at the receiving apparatus RA, and the voice frequencies originally modulating the carrier current at the transmitting apparatus TA are'reproduced at the loud speaker LS.

The inductor coils Cl and C2 are preferably air core windings of relatively large central area and are mounted on the caboose, one centered overone track rail and the other centered over the other rail. As shown in Fig. 5, the coils CI and C2 are disposed in a horizontal plane at a height of d inches which may vary from six to fourteen inches and is preferably of the order of, ten inches above the top of the rail. As previously stated, we have discovered that inductor coils Cl and C2 when so constructed and so positioned inductively receive telephone current energy with minimum annoyance due to the ma netic field created by the propulsion current. In Fig. 4 there is illustrated the inductive relationship as it appears to exist between the inductor coils Cl and C2 and the magnetic field created about the rails of the tracks of Fig. 3 by the telephone current supplied to the rails of the track |W from the trans- .mitting apparatus TA of locomotive 20. It is to telephone communication is accomplished between the locomotive and the caboose of the train FT of Fig ..3 through the medium of the apparatusesTA and RA and the track rails, the receiving apparatus beingfree to a large degree at least from noise energy prevailing in the electrified zone due to the characteristics of the inductor coils. .It is clear that by providing transmitting apparatus on the caboose of the train FT and receiving apparatus on the locomotive two-way. telephone communication can be accomplished.

In territories such as are shown in Figs. 1 and 3 where double rail track circuits are used, an advantage is obtained in the telephone noise ratio when the inductor coils Cl and C2 are connected to oppose each other in response to a uniform vertical magnetic field. This connection allows the electromotive forces induced in the two coils to aid when the telephone currents in both rails of the track occupied are in phase and in the same direction as is usually the case with a train on the track. In electrified territory where single rail track circuits are used, however, we have 7 found better results to be obtained when the inductor coils-are connected to add their effects as produced by a uniform vertical magnetic field. Thus, the preferred connection for the inductor coils depends upon the track characteristics.

Again, we have found some advantage in the telephone noise ratio on the outer track of a four-track road resultsfrom a slight tilt of the inductor coils, about 20 from the horizontal toward the outside of the track, as illustrated in Fig. 6. In Fig. 6, the inductor coils are otherwise kept in the same position described hereinbefore. "However, good results can be obtained on the outside tracks of a four-track road with the coils exactly horizontal, as illustrated in Fig. 5.

Referring'to Figs. 7, 8 and 9, the caboose 2| is equipped with two pairs'of inductor coils. Coils Cl and C2 of one pair are mounted on the caboose in the manner already explained. Inductor coils C3 and C4 of the other pair are mounted on the caboose roof to one side of the cupola. The coils C3 and C4imay be arranged one on one side of the cupola and the other on the other side of the cupola, or both may be placed on the same side, as desired. We have found, however, that in steam territory a preferred arrangement for such roof coils is for the coils to be disposed on the same transverse center line and each an equal distance from the longitudinal center line of the caboose. The entire receiving apparatus on the caboose would preferably be symmetrically disposed about the center line of the caboose, as illustrated in Fig. 9. The coils C3 and C4 are preferably air core windings and are positioned each in a vertical plane and are series tuned by condensers located adjacent each coil. p

A double-pole double-throw switch 40 is provided for selectively connecting the two pairs of inductor coils in. the input circuit of the receiving apparatus RA. Looking at Fig. 7, the coils Cl and C2 are included in the .input circuit when the switch 40 is closed to the left. With the switch 40 closed to the right, the roof coils C3 and C4 are included in the input circuit.

It follows that with the switch 40 closed to the left as viewed in Fig. '7 the receiving apparatus of the caboose 2| is conditioned for best operation when the caboose is to be operated over electrified territory. With the switch 40 closed to parting f-rom-the spirit and scope of our invention.

Having thus described our invention, what we claimis: V p

1-. In combination, a railway track, a train, transmitting apparatus located along the track to cause a periodic communication current to flow in the track rails, receiving apparatus responsive tosuch current mounted ona vehicle of thet'rain,

an inductor mounted on saidvehicle directly above one of the track rails, said inductor disposed with its axis vertical and positioned at a height of the order of ten inches above the topof the rails-for inductively receiving an electron ctivef'orce due to the currentsupplied to the rails. by the transmitting apparatus with minimum interference from extraneous magnetic fields, andcircuit means to'connect said receiving apparatus. v

2; In combination, a railway traclgja train, transmitting apparatus located along the track to causeaperiodic conununica'tion current to flow inthe track rails, receiving apparatus responsive to such current mounted on a vehicle of the train," an. inductor mounted on said vehicle comprising two coils of relatively large central areasand one. of, which is centrally positioned above one. rail and the other one of which is centrally positioned above the other rail, said coi'ls'dis'posed in a hori-' zontal planefor minimum induction to the rail directly beneathland for relatively large induction to the. other rail. of "the track and said coils carried; at a height of the order of ten inches above the top of the rails for small inductive response to noise energy magnetic fields existing about the rails and effective inductive response to the magnetic field caused by the current flowing in the rails due to the transmitting apparatus, and circuit means to connect said inductor coils with the receiving apparatus.

3. In combination, an electrified zone of a railway track the track rails of which are bonded to serve as a return circuit for propulsion current, a train, transmitting apparatus located along the track to cause a periodic communication current to flow in the track rails, receiving apparatus responsive to such communication current mounted on a vehicle of the train, two inductor coils mounted on said vehicle one directly above one rail and the other directly above the other rail, said coils disposed in a horizontal plane at a height of the order of ten inches above the top of the rail for minimum inductive response to the propulsion current and effective inductive reinductor with the Sponse to the communication current flowing in V the rails due to the transmitting apparatus, and circuit means to connect said coils with the receiving apparatus.

4. In combination, an electrified zone of a multi-track railway the track rails of which are bonded and cross connected to serve as a coimnon return circuit for propulsion current, a train occupying one of the tracks, a source of propulsion current for operating the train, communication equipment including transmitting apparatus operative to supply a periodic communication current mounted on one vehicle of the train and v 5 receiving 'apparatus responsive to such communication current mounted on a second vehicle of thetraim-"ineans to-couplc the-transmitting apparatuswithi the rails -tocause communication-current to flow in therails of the tracks, two=inductor coils meuiited onsaid second vehicle one over one ra l-Fahd the other over the other rail; said coils disposed in a'horizontal plane'at aheight of the order o'f'teni'nches"forfininimum inductiveinfluence-due t the propulsion current andto inductively r j eivingan'elcctromotive force in response 'to-thc communi'catio'n current flowing in the rail'sof the different tracks due to the trans mitting appar-atus, and circuit 'ineans to connect said inductor coils with the receiving apparatus. 5 ."In =conibination; an electrified zone of a multi-track railway the track rails of which are bonded. and crass; connected-toscrve asa return circuit for propulsion'xcurrent and each track providedwith a trolleyfwire, a generatorconnected' withisaid' trolley wiresand said return rail circuit to supply an alternating current for operaun namsj over saidzoneand whichcurrent tendsfteecualize in the rails of the different tracksfa train on one o-fsaid-tracks; communicanon-equipment including transmitting apparatus mounted on one-wehi'cle- 'of' the train and receiving apparatus mountedona second: vehicle of the train, said transmitting apparatus operative to supply"a carrierftelephone current and said receiving apparatusoperative to A demodulate and reproduce the voicefrequencies. of'such. telephone current, meansto couple the'transmitting 'appaferent trackfsJiby virulent th distributedirail-toground conductance and: the cross connections,

and arm u t'for aid receiving apparatus including two" inductor coils mounted-on said;

secondyehicleonecentered over one rail andithe other-"centeredoverthe' other rail for inductively receiving an electro-motive force due to the distribution of the telephone current in the rails of the difierent tracks, and said coils disposed in a horizontal plane at a height of six to fourteen inches above the top of the rails to effect best telephone to propulsion current noise energy ratio.

6. In combination, an electrified zone of a multi-track railway the track rails of which are bonded andcross connected to serve as a return circuit for propulsion current and. each track provided with a trolley wire, a generator connected 7 with said trolley wires and said return rail circuit to supply an alternating current for operating trains over said zone and which current tends to equalize in the rails of the difierent tracks, a train V on one of said tracks, communication equipment including transmitting apparatus located along the tracks and receiving apparatus mounted on a vehicle of the train, said transmitting apparatus operative to supply a carrier telephone current and said receiving apparatus operativeto demodulate and reproduce the voice frequencies of such telephone current, means to couple the transmitting apparatus to the track rails to cause the telephone current to be distributed in the rails of the different tracks; and an input circuit forsaid receiving apparatus including an inductor comprising two air core windings of relatively large central areas, said windings mounted on said vehicle one centered over one rail with its axis vertical and the other centered over the other rail with its axis vertical and each winding carried at a heightof the order of ten inches for receiving an electromotive force due to the telephone current distributed over the rails of the difierent tracks with a minimum amount of noise energy due to the distribution of the propulsion current over the rails.

7. In combination, an electrified zone of a. multi-track railway the track rails of which are bonded and cross connected to serve as a return circuit for propulsioncurrent and each track provided with a trolley wire, a generator connected with said trolley wires and said return rail circuit to supply an alternating current for operating trains over said zone and which current tends to equalize in the rails of the different tracks, a train on one of the outside tracks of said tracks, communication equipment including transmitting apparatus mounted on one vehicle of the train and receiving apparatus mounted on a vehicle of the train, said transmitting apparatus operative to supply a carrier telephone current and said receiving apparatus operative to demodulate and reproduce the voice frequencies of such telephone current, means to couple the transmitting apparatus to the track rails to cause the telephone current to be distributed in the rails of the different tracks by virtue of the distributed rail-to-ground conductance and the cross connections, and an input circuit for said receiving apparatus including two air core coils of relatively large central areas mounted on said vehicle one centered over one rail and the other centered over the other rail, and said coils positioned at a height of the order of ten inches above the top of the rails and tilted about 20 from the horizontal toward the outside of the track for inductively receiving an electromotive force due to the distribution of the telephone current in the rails of the different tracks with bestjtelephone to propulsion current noise energy ratio.'

V 8. In combination, a railway vehicle adaptable of operation over either steam or electrified territories of a railway, receiving apparatus mounted on said vehicle operative to reproduce the voice frequencies of a telephone current, a first and a second inductor mounted on said vehicle, said first inductor mounted relatively high on the vehicle and in a vertical plane for inductively receiving an electromotive force due to such telephone current flowing inthe track rails in steam territory, said second inductor mounted in a horizontal plane directly over a track rail at the height of six to fourteen inches above the top of the rail for inductively receiving an electromotive force due to telephone current flowing in the track rails in electrified territory, and means to connect either said first or said second inductor with the receiving apparatus.

9. In combination, a railway vehicle adaptable of operation over either steam or electrified territories of a railway, receiving apparatus mounted on said vehicle operative to reproduce the voice frequencies of a telephone current, a first and a second pair of inductor coils mounted on said vehicle, said first pair of coils mounted relatively high on the vehicle and in a vertical plane for inductively receiving an electromotive force due to such telephone current flowing in the rails in steam territory, said second pair of coils mounted one over one rail and the other over the other rail and each disposed in a horizontal plane at a height of the order of ten inches for inductively receiving an electromotive force due to the telephone current flowing in the rails in electrified territory with minimum interference due to the propulsion current, and means for connecting either the coils of the first pair in series or the coils of the second pair in series with said receiving apparatus. 1

WILLARD P. PLACE. PAUL N. BOSSART. LARS O. GRONDAHL. 

